1. Field of the Invention
The present invention relates to a sheet inversion device provided in a copier that requires the alignment of pages in a multiple-copy process or the inversion of a sheet in double-side printing.
2. Description of the Related Art
A general example of this type of sheet inversion device is disclosed, for example, in Japanese Unexamined Patent Publication No. Hei 7-232848. In the inversion structure shown in FIG. 24, a feed-in roller 242 and a feed-out roller 243 both contact the circumferential outer surface of a clockwise rotating intermediate roller 241. When a sheet 244, sandwiched between the intermediate roller 241 and the feed-in roller 242, is delivered, the sheet 244 is fed along a guide plate 245 after being deflected obliquely upward by an opposed belt 246, and defines an inclined inversion path 247 between the guide plate 245 and the opposed belt 246.
When the trailing end of the sheet 244 is removed from between the intermediate roller 241 and the feed-in roller 242, gravity causes the trailing end (lower end) of the sheet 244 to hang downward in the drawing. At this time, while the opposite belt 246 is rotated counterclockwise, the trailing end (lower end) of the sheet 244 is guided to and grasped by the intermediate roller 241 and the feed-out roller 243, and is fed in the opposite direction.
However, because the conventional structure depends on gravity to shift sheets 244 introduced, along the inclined inversion path 247, from the feed-in direction, and to position them for pickup and removal by the intermediate roller 241 and the feed-out roller 243, the shifting of the sheets 244 for pickup by the intermediate roller 241 the feed-out roller 243 is not precisely performed and feeding failures occur.
Therefore, a sheet inversion device has been provided, wherein an inversion roller, which is rotated in the direction opposite to the sheet feed-in direction, and a pressing guide member, which applies a feed-in load to a sheet, are provided inside the inversion path, so that the inversion of the sheet does not depend on gravity.
However, in this case, since the inversion roller is rotated in the direction opposite to the sheet feed-in direction, the inversion roller applies the delivery force to the sheet in the opposite direction. As a result, if a sheet is thin, the leading edge of the sheet is bent or compressed when a strong holding pressure is applied by the inversion roller and the pressing guide member. And if a sheet is thick, a weak holding pressure applied by the inversion roller and the pressing guide member will not hold the sheet securely, and when the sheet is conveyed upward, its own weight may cause it to fall.
Additionally, for this device, while the sheet 244 is inverted, i.e., when the sheet 244 is released from the rollers 241 and 242 and before it is again sandwiched between the rollers 242 and 243, the sheet 244 is free. Therefore, when the free sheet 244 drops of its own weight, while the feeding force of the belt 246 acts on it, the sheet 244 is skewed and is obliquely discharged. When stapling is required in the following process, sheets discharged in the skewed state would be stapled. To prevent this, the discharged sheets must be manually aligned, and when double-side copying is performed, images will be copied onto sheets that are skewed during the inversion process, so that the copying performance is deteriorated.
Since a large inertial feeding force is produced when a sandwiched sheet is linearly fed, and since the leading edge of a sheet tends bend when it contacts another member, it is an object of the present invention to provide a sheet inversion device that includes a retraction structure that can eliminate an overload applied to the leading edge of a sheet, so that the sheet can be smoothly inverted, regardless of its thickness.
It is another object of the present invention to provide a sheet inversion device that does not skew sheets, even when the sheets are free and feeding force is applied, and that can align sheets as they are discharged.
According to a first aspect of the present invention, a sheet inversion device for reversing the surfaces of a sheet that has been fed into said sheet inversion device, comprises:
a first roller, located at the start of an inversion path in the direction in which a sheet is input or output along said inversion path, that rotates in only one direction;
a second roller, arranged parallel to said first rollers, that rotates with said first roller so as to feed said sheet into said inversion path;
a third roller, located in parallel to said first rollers on the opposite side of said first rollers from said second rollers, that rotates with said first rollers to feed out and discharge said sheet from said inversion path;
a fourth roller, located inside said inversion path, for applying a feeding force, in a discharge direction relative to a sheet feeding force applied by said first and second rollers, that causes said fourth rollers to slip across said sheet; and
a pressing and guide member, for applying, with said fourth roller, a sheet pressing force that resists the advance of a sheet that is being fed;
wherein a pressing face of said pressing and guide member has the same arced shape as has the circumferential outer face of said fourth roller.
According to a second aspect of the present invention, in addition to the arrangement of the first aspect, said pressing guide member comprises a first member for applying a pressing force and a second member having the same shape as the outer circumferential face of said fourth roller; and wherein said second member is permitted to pivot in the feeding direction at a fulcrum position whereat said second member is supported by said first member.
According to a third aspect of the present invention, in addition to the arrangement of the second aspect, an intermediate portion of said second member is located at said fulcrum position, and an elastic member for adjusting a pivoting distance is employed to couple together said first member and the rear portion of said second member.
According to a fourth aspect of the present invention, a sheet inversion device for reversing the surfaces of a sheet that has been fed into said sheet inversion device, comprises:
a first roller, located at the start of an inversion path in the direction in which a sheet is input or output along said inversion path, that rotates in only one direction;
a second roller, arranged parallel to said first rollers, that rotate with said first roller so as to feed said sheet into said inversion path;
a third roller, located in parallel to said first rollers on the opposite side of said first rollers from said second rollers, that rotates with said first rollers to feed out and discharge said sheet from said inversion path;
a fourth roller, located inside said inversion path, for applying a feeding force, in a discharge direction relative to a sheet feeding force applied by said first and second rollers, that causes said fourth rollers to slip across said sheet; and
urging means for pushing said pressing guide member against said fourth roller upon the application of a force by said pivoting lever.
According to a fifth aspect of the present invention, sheet inversion device for reversing the surfaces of a sheet hat has been fed into said inversion device, comprises:
a first roller, located at the start of an inversion path in the direction in which a sheet is input or output along said inversion path, that rotates in only one direction;
a second roller, arranged parallel to said first rollers, that rotate with said first roller so as to feed said sheet into said inversion path;
a third roller, located in parallel to said first rollers on the opposite side of said first rollers from said second rollers, that rotates with said first rollers to feed out and discharge said sheet from said inversion path;
a fourth roller, located inside said inversion path, for applying a feeding force, in a discharge direction relative to a sheet feeding force applied by said first and second rollers, that causes said fourth rollers to slip across said sheet;
a rotary member, which is coaxially arranged with the rotary shaft of said fourth roller and which has a contact face that covers a part of said fourth roller, that is rotated and retracted when a driving force applied to a sheet being fed in is applied in turn to said rotary member as the leading edge of said sheet being fed in is pressed against said contact face; and
a pressing guide member for which, when rotation of said rotary member is halted, controls the position of said rotary member so as to suppress the pressing force exerted against said fourth roller, and for which, when said rotary member rotates and retracts, said position control is canceled so that the pressing force can be exerted with that of said fourth roller.
According to a sixth aspect of the present invention, in addition to the arrangement of one of the first to fourth aspects of the present invention, said pressing guide member includes an elastic retraction control member for, when a thin sheet is being fed in by said first and said second said rollers, retracting upon the application of a force produced by the advance of said thin sheet, and for, when a thick sheet is being fed in by said first and said second rollers, retracting upon the application of a force produced by the advance of said thick sheet, while increasing the power of an elastic support force in accordance with the thickness of said sheet.
According to the present invention, for sheet inversion, a sheet, introduced to and sandwiched between the first and the second rollers at the beginning of the inversion path, is fed into the inversion path, and its leading edge is advanced to and inserted between the fourth roller and the pressing guide member. At this time, the sheet is being fed along the inversion path while the pressing guide member applies a pressing force to counter the force exerted to advance the sheet. Then, when the trailing edge of the sheet is freed from the clasp of the first and the second rollers, and the entire sheet has been fed into the inversion path, a feeding force exerted in the opposite direction by the fourth roller is applied to the sheet, which is thereafter delivered in the feed-out direction to the first and the third rollers. In this fashion, the sheet is inverted and is discharged from the inversion path.
In this case, since the pressing face of the pressing guide member has the same arced shape as has the circumferential outer face of the fourth roller, when a thin, comparatively weak sheet is introduced into the inversion path, as it is fed in its leading edge slides along the arc shaped face of the guide member and the circumferential outer face of the fourth roller. Thus, the deflection of the pressing guide member is small, and an appropriate pressing force is applied to the thin sheet.
On the other hand, since in the feed-in direction a strong linear force is projected by a thick, heavy sheet as it is fed into the inversion path, and its leading edge pushes down and thereby increases the displacement of the pressing guide member and the strength of the pressing reaction force, a satisfactorily strong pressing force can be obtained for the thick sheet. As a result, it is possible to provide a variable pressing force that is exerted in consonance with the thickness of a sheet, so that a thin sheet is prevented from being bent or from being compressed, and a thick sheet can be securely held and smoothly inverted.
Furthermore, when the pressing guide member is divided into a first member that exerts a pressing force and a second member that is shaped to fit the circumferential outer face of the fourth roller, and when the second member is provided so that it can pivot like a teeter-tooter in the feeding direction at the fulcrum point, whereat it is supported by the first member, the second member is pivoted by the application of the force produced by the advancement of the sheet, and consequently, its leading edge is retracted, separated from the opposite fourth roller, and its rear end is pushed against the sheet. Therefore, during the process performed to feed the sheet past the fourth roller, at which time the greatest load is supposed to be imposed on the sheet, when the leading edge of the sheet passes the fourth roller, the rear end of the second member is pushed against the sheet, so that no load is imposed on the leading edge of the sheet, and a stable feeding operation can be performed without the sheet being bent or deformed.
In addition, in a case wherein the intermediate portion of the second member is provided at the fulcrum, and wherein an elastic member for adjusting the pivoting distance is employed to connect the rear end of the second member to the first member, when a thin sheet is fed in, the elastic member that elastically supports the second member comparatively weakly operates the pressing guide member and permits it to pivot, so that the thin sheet is appropriately pressed against and guided. Then, when a thick sheet is fed in, the first member performs the original guiding operation so as to appropriately press against and guide the thick sheet. As a result, a broad application range extending from a thin sheet to a thick sheet can be obtained for the sheet passing process.
Furthermore, in the case wherein there is provided a pivoting lever, which pivots and retracts upon the application of force produced by the advance of the sheet that is fed in by the first roller and the second roller, and an urging means for pushing the pressing guide member, upon the application of the pivoting force produced by the pivoting lever, an interlocking structure can be obtained. That is, the movement of the pivoting lever is interlocked with the advance of the sheet that is fed in along the inversion path, and in consonance with this movement, the urging means pushes the pressing guide member against the fourth roller. Therefore, as a thin sheet is fed in, a weak force is generated by the advance of the thin sheet and a small pressing force is exerted, while as a thick sheet is fed in, a strong force is generated by the advance of the thick sheet and a large pressing force is exerted. As a result, an appropriate pressing force can be automatically obtained in consonance with the thickness of a sheet that is handled.
Moreover, assume that in the above case there were provided a rotary member, positioned coaxially with the rotary shaft of the fourth roller, that could cover a part of the fourth roller and that had a contact face that would contact the leading edge of a sheet, so that the force produced by the advance of the sheet would rotate and retract the rotary member; and there were provided a pressing guide member that, when the rotation of the rotary member was halted, could adjust the position of the rotary member so as to suppress the pressing force exerted by the fourth roller, and that, when the rotary member was rotated and retracted, canceled the positional relationship with the rotary member and permitted a pressing force to be exerted by the fourth roller. In this case, the leading edge of a sheet that is fed in along the inversion path contacts the contact face of the rotary member but does not contact the fourth roller that is rotating in the feed-out direction. Thus, when the sheet is fed in, a load in the feed-out direction is not imposed by the fourth roller, and the sheet is fed smoothly. Thereafter, when the leading edge of the sheet pushes the rotary member away and passes the fourth roller, the rotary member rotates and retracts and clears the outer circumferential surface of the fourth roller. The sheet then receives the feed-out force through its contact with the outer circumferential face of the fourth roller, and when the application of the feed-in force is halted, the sheet is fed in reverse in the feed-out direction.
Also, assume that in the above case the pressing guide member that includes the elastic retraction control member is provided, and that when a thin sheet is fed in by the first and the second rollers, the pressing guide member is simply retracted upon the application of the force produced by the advance of the thin sheet, while when a thick sheet is fed in, the pressing guide member is retracted upon the application of the force produced by the advance of the thick sheet and the strength of the elastic support force is increased in consonance with the thickness of the sheet. In this case, when the thin sheet is fed in, the pressing guide member performs an ordinary pressing operation and appropriately presses and guides the thin sheet, and when the thick sheet is fed in, the elastic retraction control member increases the elastic support force of the pressing guide member and appropriately supports the thick sheet. As a result, an appropriate pressing force can be exerted in consonance with the weights of a thin sheet and a thick sheet.
According to a seventh aspect of the invention, a sheet inversion device for inverting a sheet and discharging the inverted sheet, comprises:
first rollers, located at the start of an inversion path in the direction in which a sheet is input or output along the inversion path, that rotate in only one direction;
second rollers, arranged parallel to the first rollers, that rotate with the first rollers so as to sandwich the sheet between them and to feed the sheet into the inversion path;
third rollers, located in parallel to the first rollers on the opposite side of the first rollers from the second rollers, that rotate with the first rollers to feed out and discharge the sheet from the inversion path;
fourth rollers, located inside the inversion path, for exerting a feeding force, in a discharge direction relative to a sheet feeding force exerted by the first and second rollers, that causes the fourth rollers to slip across the sheet; and
sheet control plates, located inside the inversion path, for holding the sheet at a predetermined position along the inversion path.
According to an eighth aspect of the invention, in addition to the arrangement of the seventh aspect, the sheet control plates are provided as pairs on both sides in consonance with the width of a sheet. In accordance with the positioning shift of the sheet that is delivered into the inversion path, the individual sheet control plates are moved horizontally, and are thereafter urged by urging means to return the sheet control plates to predetermined positions when the sheet is discharged.
According to a ninth aspect of the invention, in addition to the arrangement of the seventh aspect, the pairs of the sheet control plates are coupled in accordance with the width of the sheet, and are supported so as to be horizontally movable in consonance with the positioning shift of the sheet that is fed into the inversion path.
According to a tenth aspect of the invention, in addition to the arrangement of the ninth aspect, the sheet control plates are urged by the urging means so that the sheet control plates are returned to predetermined positions when the sheet is discharged.
According to an eleventh aspect of the invention, in addition to the arrangement of the seventh aspect, the pairs of the sheet control plates are provided in consonance with different sheet widths. The pairs of the sheet control plates are rotatably supported, so that when a sheet advances onto the corresponding pair of the sheet control plates, the pair of the sheet control plates are retracted.
According to a twelfth aspect of the invention, in addition to the arrangement of the seventh aspect, pairs of the sheet control plates are provided in a rib-shaped arrangement in accordance with different sheet widths. As a pair of the sheet control plates is positioned outward, the pair is higher than the other pair, which is positioned inward.
According to a thirteenth aspect of the invention, in addition to the arrangement of the seventh aspect, pairs of the sheet control plates are fitted around a rotary shaft at different angles in consonance with different sheet widths. As the rotary shaft is rotated, a specific pair of the sheet control plates can be selected in consonance with the width of a sheet that is fed into the inversion path.
According to a fourteenth aspect of the invention, in addition to the arrangement of the thirteenth aspect, a drive force is transmitted to the rotary shaft from a rotary shaft of the first rollers, which rotate in only one direction, via a unidirectional clutch, to which the reverse rotation of the first rollers is transmitted.
According to a fifteenth aspect of the invention, in addition to the arrangement of one of the seventh to the fourteenth aspects, each of the sheet control plates at the start of the inversion path is extended outward from the width of a corresponding sheet.
According to this invention, a sheet that is fed into the inversion path can be controlled at a predetermined position by using the sheet control plates. Thus, even when the sheet is released from the feeding rollers and is free of any feeding force, or when the feeding force in the discharge direction is applied to the free sheet by the rollers, the position of sheet that is discharged is controlled by the sheet control plates, so that skewing of the sheet is exactly prevented.
According to the eighth aspect, the sheet control plates can be individually moved and returned to their predetermined positions. Therefore, when the position of a sheet is shifted during feeding, or when the sheet is skewed due to a feeding failure, such a sheet can be accepted, and can also be returned to a predetermined position by the urging force. Thus, a sheet can be aligned at predetermined position, and can be discharged after its posture has been corrected.
According to the ninth aspect, since the pair of sheet control plates can be supported so that they can be moved horizontally, the sheet control plates can be moved and can cope with a sheet that is fed in while its position is shifted. The positioning of the sheet can be controlled when the sheet is accepted, and thereafter the sheet can be discharged.
According to the tenth aspect of the invention, the pairs of sheet control plates that are moved horizontally are urged to return to their predetermined positions, so that a sheet can be discharged from the center position.
According to the eleventh aspect of the invention, the sheet control plates are rotatably supported so that they can be retracted from the inversion path. In the process for the inversion of multiple sheets having different widths, when a wide sheet is fed in and runs across sheet control plates that correspond to a narrow sheet, these sheet control plates are retracted from the inversion path, so that the wide sheet can be precisely controlled by the corresponding sheet control plates. Therefore, when multiple types of sheets are employed, these can be precisely controlled,at corresponding locations.
According to the twelfth aspect, as the pair of sheet control plates in a rib-shaped arrangement is located outward, the height of the pertinent pair is increased. Therefore, as well as in the fifth aspect, when multiple sheets having various widths are employed, a wide sheet can runs across to the sheet control plates that correspond to a narrow sheet, and can be precisely controlled by the corresponding sheet control plates. As a result, even when a plurality of sheet type are employed, the positioning of all the sheets can be exactly controlled.
According to the thirteenth aspect of the invention, the sheet control plates are fitted around the rotary shaft in consonance with various sheet sizes, and appropriate plates are selected to control a sheet. Therefore, only one pair of sheet control plates is projected into the inversion path, and no other, unnecessary control plates are present, so that the chance that a sheet will be hung up on unnecessary sheet control plates is completely eliminated.
According to the fourteenth aspect, a driving force is transmitted to the above rotary shaft from the first roller that rotates in only one direction for feeding in and feeding out a sheet, so that the rotary shaft is rotated in the opposite direction. Thus, a special drive source for controlling the rotary shaft is not required, and the structure can be simplified.
According to the fifteenth aspect of the invention, the side of each sheet control plate that corresponds to the start of the inversion path is extended outward the width of a sheet. Thus, even when the position of a sheet that is fed in is shifted slightly, the sheet can be accepted, so that the chance that a sheet will be jammed in the sheet control plates due to a positioning shift can be completely eliminated.